Chlamydiaceae is a family of obligate intracellular parasites. All members share a common developmental cycle. Chlamydia infect a wide range of vertebrate host, particularly humans. Chlamydia trachomitis is one of the two recognized species of Chlamydia. Human infections caused by C. trachomitis are widespread. This species is one of the most common cause of sexually transmitted disease in the world. It is also one of the main causes of infertility in humans.
The frequency of Chlamydia trachomatis infections has risen dramatically in the past 20 years. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Chlamydia trachomatis strains which are resistant to some or all of the standard antibiotics. This has created a demand for both new anti-microbial agents and diagnostic tests for this organism.
Transfer RNA ("tRNA") synthetases have a primary role in protein synthesis according to the following scheme: first, Enzyme+ATP+AA Enzyme.AA-AMP+Ppi, followed by Enzyme.AA-AMP+t-RNA Enzyme+AMP+AA-t-RNA, in which AA is an amino acid, ATP and AMP are the triphosphated and monophosphated forms of adenosine, respectively, and Ppi is inorganic pyrophosphate. Inhibition of this process leads to a reduction in the levels of charged t-RNA and this triggers a cascade of responses known as the stringent response, the result of which is the induction of a state of dormancy in the organism. As such, selective inhibitors of bacterial t-RNA synthetase have potential as antibacterial agents. One example of such is mupirocin, which is a selective inhibitor of isoleucyl t-RNA synthetase.
Clearly, there is a need for factors, such as the novel compounds of the invention, that have a present benefit of being useful to screen compounds for antibiotic activity. Such factors are also useful to determine their role in pathogenesis of infection, dysfunction and disease. There is also a need for identification and characterization of such factors and their antagonists and agonists which can play a role in preventing, ameliorating or correcting infections, dysfunctions or diseases.
The polypeptides of the invention have amino acid sequence homology to a known Escherichia coli cysteinyl tRNA synthetase protein. See Eriani et al., Nucleic Acids Res., 19:265-269 (1991); HOU et al., Proc. Natl. Acad. Sci USA, 88:976-980 (1991), AVALOS et al., FEBS LETT., 286:176-180 (1991); and SwissProt Accession No. P21888.